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A Brief History of Insect Control

Long before environmentalism, Charles Valentine Riley had a problem with pesticide.

Spraying the capitol with pesticide, 1886.

In science, good ideas often trump great ones. Take, for instance, Charles Valentine Riley, the most prescient scientist of whom you’ve never heard. The man had a great idea. Then came Leland Howard, his prickly and calculating successor. He had the good one.

These men were late nineteenth-century entomologists, a humble vocation by the standards of the day. But the U.S. Department of Agriculture—new then, having been formed in 1862—asked them to accomplish something not so humble: they were to learn everything there was to know about agricultural pests, and then to destroy them. The intended beneficiaries of this project were panicked farmers whose fields were being decimated by insect invasions. Riley and Howard were charged with exterminating the very creatures they studied. If the irony registered, they never said so.

Riley was the older of the two gentlemen. He’d assumed leadership of the U.S. Entomological Commission in 1876 after spearheading the country’s first Grasshopper Commission. His big idea—the great one—was to merge the observational folk-wisdom of everyday farmers with the financial largesse of the federal government to help insects kill insects. Biological control, we now call it. If the concept of exterminating insects with insects seemed moony, American farmers were game. They’d seen it happen on the ground and they were desperate. Between 1860 and 1900—a time when agriculture began to pursue high-yielding monoculture in earnest—armies of chinch bugs, locusts, San Jose scales, boll weevils, Colorado potato beetles, and Hessian flies capitalized on the smorgasbord, moving steadily eastward and shredding the foodscape with biblical power. One Illinois farmer reported that there were so many locusts in his fields that “the ground seemed to be moving.” Pick up an agricultural report from the period—you know, just pick one up!—and you’ll find that an apocalyptic strain of agrarian rhetoric echoed across America’s amber waves of grain.

I’ve read nearly every word Riley wrote, at least every available report and letter, and my overwhelming impression is that the guy was one charming cat. He rode his bike all over D.C. for exercise. He had six kids and doted on them. Like many entomologists, he was a brilliant illustrator of insects. When he taught entomology classes at the University of Missouri in the 1870s, he was so thrilled to be talking shop that he would draw insects on the board with both hands at once. He grew his hair into a cascade of curls and his students adored him. I have no hard proof, but there was something about Riley’s zest for life in general—and for insect life in particular—that dissuaded him from the easy answer to the insect problem, the one that the power brokers of the day wanted: chemicals.

Riley, 1876.

Riley was instinctively wary of these new concoctions—amateurish compounds of arsenic and lead and kerosene—being sprayed and dusted over arable land and healthy soil. He had never, he wrote, “had much faith in the application to the plant or the insect of any chemical mixture.” It was the insects’ natural enemies, by contrast, “that carry on their good work most effectually.” (In this respect Riley stood on the shoulders of his mentor, Benjamin Walsh, an outspoken entomologist who deemed chemical washes “hellbroths” and spent columns of ink lambasting them in The American Entomologist.) Riley wasn’t categorically opposed to the available sprays of the day—Paris Green and London Purple, to name the most popular—but he decided that it was in everyone’s best interest to keep calm, do some fieldwork, and see if nature might do the job first. Charles Darwin, for one, sent him a little fan note.

Riley knew his way around a farm. He cut his teeth in the wheat fields of the Midwest, where he worked himself to the point of exhaustion helping farmers manage a microscopic root insect called phylloxera. His proposed solution was to introduce mites that “prey extensively on this root-inhabiting type.” The results were decent, but no knockout. Riley drew upon this research to help French vintners, whose vineyards were being devastated by phylloxera; he suggested that they graft a native grape onto a phylloxera-resistant American vine. This advice saved France’s wine industry. In 1884 Riley had a French Grand Gold Medal pinned to his lapel.

An illustration by Riley from the 1885 United States Entomological Commission Report on the Cotton Worm.

Then he hit pay dirt at home. In 1886 an Australian insect called the cottony-cushion scale—an adult female looks like a tiny puff of cotton—came over on some acacia tree saplings and sent the nation’s orange industry into a tailspin, invading California’s citrus groves. Riley, who was by this time head of the Department of Agriculture’s entomology division, sent an insect collector to find the scale’s natural predators. By January 1889, the collector had an answer: Vedalia beetles. California entomologists bred and released 10,555 of them into California’s orange groves. Within months the cottony-cushion scale had effectively vanished and the industry recovered.

It was the world’s first commercial-scale triumph of biological control. The New York Times called Riley’s plan “a complete success,” and Riley, beside himself, began centering the Division of Entomology’s research agenda on the promise of biological control. But those plans came to a tragic halt on September 14, 1895. Riding his bike to the Smithsonian to look at butterflies, Riley hit a paving stone, pitched over the handlebars, and died from a head injury. (Oddly enough, years earlier his mentor, Walsh, had been run over by a train.)

Riley’s sketches of the Vedalia beetle.

Leland Howard, Riley’s longtime second-in-command—openly disgruntled for having been treated “like a clerk”—took charge of the Division of Entomology. His training took place in a Cornell laboratory rather than a Missouri wheat field, and he quickly developed different ideas about effective insect control. This was the Progressive Era, and Howard, a good progressive, believed that problems should be identified, experts amassed, and the most potent solutions applied. For a federal entomologist accountable to the general public, this meant one thing: chemicals.

Riley’s drawings of the Colorado Potato Beetle.

To be fair, Howard gave biological control a shot. Soon after assuming Riley’s position, he targeted the gypsy moth, whose larvae had come to Massachusetts by way of a French suitcase back in the 1860s. By the 1890s, they were denuding trees throughout New England. Howard traveled to Europe and researched the moth’s natural enemies. He returned with several possible predators, released them, and prayed for success—but to no avail. He never found his Vedalia beetle. The gypsy moth continued to decimate the region’s towering hardwoods, leaving Howard, as one critic put it, with “egg on his face.”

So Howard, suddenly attuned to the political benefits of expediency, did something remarkably savvy. He promoted insecticides by highlighting a far more pervasive danger: mosquitoes, which had, after the 1900 discovery that they were linked to malaria, become the preeminent pest in America. Concern for the nation’s agricultural prosperity yielded easily to public health anxieties, and Howard was well aware of the transition—he bombastically announced the onset of a “mosquito plague” and quickly wrote Mosquitoes: How They Live; How They Carry Disease; How They Are Classified; How They May Be Destroyed. In that volume, he made an airtight case: the only way to kill the Anopheles mosquito, and thereby to protect and serve the citizenry, was to blanket the nation with a combustible hydrocarbon mist of kerosene.

There’s no doubt that Howard was right. Kerosene worked. With the Insecticide Act of 1910, mosquito spraying became not only standardized, but also relatively safe. Then came World War I. In yet another ingeniously calculating move, Howard let the War Department know that, with mites and mosquitoes and lice endemic to trench warfare, entomologists armed with chemical sprays could be just as critical to the war effort as soldiers armed with rifles. “Warfare against insect life,” he explained, required the Division of Entomology to expand its arsenal to include benzene, carbolic acid, creosote, alkaline soaks, and sulfur baths. Medical entomology, as they called it, was born.

And surely, the thinking went, what worked in the trenches would work in the fields at home. While chemical treatments were administered in Europe, farmers in the United States—men and women burdened with provisioning the war effort—had no time to dither with the trial-and-error headache of biological control. Castor beans (used for castor oil to lubricate airplane engines), beef, and wheat showed up in ample quantities because of the arsenical compounds and cattle “dipping vats” designed to keep insects at bay. In the decade after the war, the trend continued apace: farmers fought the boll weevil with ten million pounds of carbon arsenate dust and dropped bombs of Paris Green from airplanes and blimps over corn fields. An arsenic-based mosquito larvicide came to market, and companies such as DuPont and the Hercules Powder Company began to lure farmers into the quick-fix fold. A kind of path dependency set in.

By the time Leland Howard retired, in 1927, the United States was a full-fledged insecticide nation. When he died in 1950, DDT had replaced his career-launching kerosene as the mosquito killer of choice. The last vestiges of Riley’s biological-control regime were fading from the public memory. And wouldn’t you know it? In his retirement, Howard took up cycling.